Mobile communication system making use of ISDN switched network

Abstract: Base stations are connected to subscriber lines of neighboring ISDN local switches, and mobile subscriber connection control equipment connected to the subscriber line of a particular ISDN local switch manages mobile subscriber data register equipment. Connection of a call which originates from or terminates at a mobile station, registration of the location of the mobile station, and channel switching process during service are performed by way of the mobile subscriber connection control equipment using an ISDN subscriber interface.

Description: Background of the Invention Field of the Invention: This invention relates to a mobile communication system, and more particularly to a digital mobile communication system which makes use of an ISDN switched network. Description of the Prior Art: Conventionally, a mobile communication system is constructed with a switch for exclusive use for mobile subscribers. For instance, in order to perform a connection process of a call which is originated or terminated between a mobile subscriber which uses a mobile station and another subscriber of a fixed network, a switch for exclusive use (visitor mobile telephone switch) is first provided for each of the base stations located in a prescribed area, and these switches are connected to the fixed network (routing switched network) by way of gateway mobile telephone switches (Document 1 and Document 2). Document 1: Kota Kinoshita, "Technique Supporting Digital Mobile Telephones - System Network Implementation Technique," Journal of the Electronic Information Communication Society of Japan, Vol. 73, No. 8, pp. 812-818, 1990. Document 2: Minoru Tanaka, "Mobile Radiocommunication System," Japanese Patent Laid-Open No. 151136/83. Fig. 6 is a block diagram showing an example of a conventional mobile telephone system disclosed in Document 1. Referring to Fig. 6, mobile station 11 has radio transmission and reception functions. Base stations 12a and 12b are connected to visitor mobile telephone switch 13 and perform radio communication with mobile station 11, and further perform call connection with visitor mobile telephone switch 13. Visitor mobile telephone switch 13 has visitor control and connection functions for mobile station 11. Gateway mobile telephone switch 14 has a routing function between visitor mobile telephone switch 13 and public telephone switched network 15 including local switch 16 to which fixed subscriber 17 is connected. Home memory station 18 is connected to visitor mobile telephone switch 13 and gateway mobile telephone switch 14, and registers the specific numbers of mobile stations and location registration information. The system of Document 2 is proposed to allow a subscriber to perform communication by way of a same terminal between different mobile radiocommunication systems such as a mobile telephone system, a portable telephone system and a cordless telephone system. Claim 1 recites a mobile telephone radio base station and a portable telephone radio base station connected to a wire communication switched network. According to an embodiment, however, base stations of the mobile telephone system and the portable telephone system are connected to switches for exclusive use for mobile telephones, and all base stations are not connected to a local switch of an ISDN switched network. In ANNUAL REVIEW OF COMMUNICATIONS, vol. 46, 1992 - 1993 CHICAGO, IL, US, pages 1008-1012, XP 000322242 K. HALLMAN ET AL. "INTEGRATING ADVANCED TECHNOLOGIES FOR A PCS TRIAL" a PCS trial in Chicago is integrating multiple radio access technologies with ISDN and the Intelligent Network. Therein, it is stated that pocket-size personal communications services (PCS) for the mass market may become a reality in the near future. The form that PCS will take depends upon the industry's understanding of the market for PCS and the emerging technical solutions. For the initial phases of the market trial, Frequency Division Multiple Access (FDMA) using time division duplexing and Cordless Telephone-2 (CT-2) Common Air Interface (CAI) protocols has been used. Later in the trial, Time Division Multiple Access (TDMA) using time division duplexing and a modified Digital European Cordless Telephone (DECT) protocol has been deployed. The TDMA system interacted to the PSTN (Public Switched Telephone Network) via Integrated Services Digital Network (ISDN) lines using existing national standard messages and protocols. The mobile communication system used in the trial comprised, among others, a Switching Control Point (SCP) for registering information regarding mobiles subscribers including subscribers numbers of the mobile subscribers, subscriber data of the mobile stations (HSID-Handset Identifier), identification numbers of mobile stations (HSDN-Handset Directory Number) and location information of the mobile stations; base stations entitled "Intelligent Base Stations" (IBS) which are connected to a subscriber line of an ISDN local switch for performing radio link control of a mobile station to connect a call which is originated from the mobile station to the ISDN switched network by way of the subscriber line; and a mobile subscriber connection control equipment, entitled "Switching Center" (PCS) which is connected to a subscriber line of said ISDN local switch for managing said mobile subscriber data register equipment (SCP) and controlling connection of a call which is originated from or terminated at a mobile station, registration of the location of a mobile station, and a channel switching process during service by way of the subscriber line. For each of the services offered during the Trial, call flows associated with the Trial architecture had been developed. A call diagram of the call flows along with a simple description of each is shown in Figure 3 of the above-mentioned article. Summary of the Invention It is an object of the present invention to provide a mobile communication system wherein all base stations are connected to neighboring local switches of an ISDN switched network, and connection of a call originated from or terminated at a mobile station, registration of the location of the mobile station and channel switching during service are controlled by mobile subscriber connection control equipment (MSCC) which is connected to a particular one or more of the local switches of the same ISDN switched network and which controls mobile subscriber data register equipment (MSDR), or in other words, a mobile communication system which is constructed in an ISDN switched network making use of an existing ISDN fixed switched network without providing a switch for exclusive use for mobile communication and which is capable of handling a channel switching request, when one of the base stations during service transmits a channel switching request signal to one of the base stations which is in control designating an adjacent base station to which one of the mobile stations desires to be connected. Present invention is defined in claim 1. Preferred embodiments are described in the dependent claims. Brief Description of the Drawings Fig. 1 is a block diagram showing an embodiment of a mobile communication system; Fig. 2 is a signal sequence diagram of the mobile communication system of Fig. 1 when a call is originated from the mobile station; Fig. 3 is a signal sequence diagram of the mobile communication system of Fig. 1 when a call is terminated at the mobile station; Fig. 4 is a signal sequence diagram of the mobile communication system of Fig. 1 when the registration of the location of the mobile station is updated; Fig. 5 is a signal sequence diagram of the mobile communication system of Fig. 1 when a radio channel is switched during communication; and Fig. 6 is a block diagram showing an example of a conventional mobile communication system. Description of the Preferred Embodiment An embodiment of the present invention is described below with reference to the drawings. Referring to Fig. 1, mobile station 1 is an equipment unit for a mobile subscriber having radio transmission and reception functions and is in use under required registration by a mobile subscriber. Base stations 2a and 2b perform radiocommunication with mobile station 1 and are connected to subscriber lines of neighboring ISDN local switch 3a so that they perform call connection with mobile subscriber connection control equipment (hereinafter referred to MSCC) 4 by way of ISDN switched network 6. Mobile subscriber data register equipment 5 is connected to MSCC 4 and registers various information regarding mobile subscribers including subscriber numbers of the mobile subscribers, subscriber data, and identification numbers and location information of mobile stations. Mobile MSCC 4 is connected to a subscriber line of ISDN local switch 3b and controls the mobile subscriber data register equipment 5 and controls connection of a call originated from or terminated at the mobile station 1. Fixed subscriber 7 is connected to local switch 3c, and the local switches 3a, 3b and 3c are connected to ISDN switched network 6. Operation of the mobile communication system of Fig. 1 is described below referring to Figs 2-5. When attempting to originate a call from mobile station 1 toward fixed subscriber 7, as shown in Fig. 2, mobile station 1 sends a call request to base station 2a, which controls mobile station 1, designating the called subscriber number N(7) and an identification number PN(1) of mobile station 1. Upon reception of the call request, base station 2a seizes local switch 3a and originates a call designating the subscriber number N(4) allocated to MSCC 4 as a terminating address and designating the designated called subscriber number N(7) as the terminating sub-address and the mobile station identification number PN(1) as the originating sub-address. MSCC 4 holds a communication line set by way of local switch 3a, ISDN switched network 6 and local switch 3b, and reads out subscriber data corresponding to the received mobile station identification number PN(1) from the mobile subscriber data register equipment 5. MSCC 4 then analyzes the thus read out subscriber data and, after it confirms that the service is available with the mobile subscriber, it originates a call to ISDN local switch 3b designating the called subscriber number N(7) as a called number. When a call is to be originated from the fixed subscriber and terminated at the mobile station as shown in Fig. 3, fixed subscriber 7 originates a call designating the subscriber number N(1) of the mobile subscriber as a destination number. ISDN switched network 6 seizes ISDN local switch 3b with the mobile subscriber number N(1), and ISDN local switch 3b seizes MSCC 4. Holding a communication line set by way of the local switch 3c, ISDN switched network 6 and local switch 3b, and using the mobile subscriber number N(1) which was designated upon seizure, MSCC 4 reads out and analyzes subscriber data of the mobile subscriber, the identification number PN(1) and location information of the mobile station 1 in use, determines at least one or more base stations 2a to be seized from the analyzed location information, and originates a call designating the mobile station identification number PN(1) as the destination sub-address and the subscriber number N(2a) allocated to base station 2a as the destination address. Base station 2a alerts mobile station 1 with the mobile station identification number PN(1) and terminates the call at mobile station 1. Updating of location registration upon movement of a mobile station proceeds in the following manner as shown in Fig. 4. If it is assumed that-base stations 2a and 2b belong to different location registration areas and mobile station 1 detects a changing of the location registration area when it moves from the location registration area of base station 2a into the location registration area of base station 2b, mobile station 1 transmits a location registration request signal to base station 2b. Base station 2b seizes local switch 3a and originates a location registration request signal designating the identification number PN(1) of mobile station 1 as an originating sub-address and the subscriber number N(4) allocated to MSCC 4 as a terminating address. MSCC 4 calculates location information based on the mobile station identification number PN(1) and the originating address N(2b) from base station 2b and effects updating of the location information in the mobile subscriber data register equipment 5. Switching between channels during communication is performed in accordance with the signal sequence illustrated in Fig. 5. It is assumed now that base stations 2a and 2b are located adjacent each other and mobile station 1 moves, during service, from the service area of the control base station 2a in control to the service area of the adjacent base station 2b. In this instance, when mobile station 1 approaches the border of the service area of base station 2a and the received electric field becomes weak, mobile station 1 transmits a channel switching request signal to the controlling base station 2a, to which mobile station 1 is then connected, adding as additional information the base station identification number CS(2b) of base station 2b to which the channel is to be switched (step A). Base station 2a designates the identification number PN(1) of mobile station 1 as an originating sub-address adding the base station identification number CS(2b), and originates a call designating the subscriber number N(4) allocated to MSCC 4 as the terminating address, sets a communication line from base station 2a to MSCC 4 and notifies the channel switching request from mobile station 1 to MSCC 4 (step B). MSCC 4 holds the communication line set between base station 2a and MSCC 4, originates a call designating the mobile station identification number PN(1) as an originating sub-address and the subscriber number N(2b) of base station 2b as the terminating address, sets a communication line from MSCC 4 to base station 2b and requests base station 2b to secure a new radio channel necessary for channel switching (step C). Base station 2b stores the identification number PN(1) of mobile station 1 and returns an alerting message to MSCC 4 to report information of the radio channel secured for channel switching to MSCC 4 (step D). MSCC 4 notifies the information of the radio channel secured for channel switching and the identification number CS(2b) of base station 2b to base station 2a using the alerting message (step E). Upon reception of the alerting message, base station 2a transmits a channel switching instruction signal to mobile station 1 to notify the information of the radio channel for channel switching to the adjacent base station 2b which is the destination of the switching (step F). Upon reception of the channel switching instruction signal including the base station identification number CS(2b), mobile station 1 effects the channel switching process based on a re-originating procedure to base station 2b (step G). Upon reception of the originating request from mobile station 1, base station 2b confirms that the received mobile station identification number is identical with the mobile station identification number PN(1) stored at step D, and transmits a message of connection adding a channel switching completion signal to MSCC 4 (step H). Upon reception of the channel switching completion report, MSCC 4 disconnects the communication line established at the time of the channel switching request from base station 2a at step B (step I), and further disconnects the communication line to mobile station 1 which has been in a connected condition to base station 2a for service until channel switching. While the embodiment of the present invention is described in detail above with reference to the drawings, connection of a call originating from or terminating at a mobile station, registration of the location of the mobile station and channel switching process during service are performed by way of mobile subscriber connection control equipment (MSCC) using an ISDN subscriber interface, and a mobile communication network is constructed in an ISDN switched network without providing a switch for exclusive use for mobile communication. The present invention can be applied also to systems wherein base stations are provided in a private branch or inside ordinary houses.

Claims: A mobile communication system which is constructed in an ISDN switched network (6), comprising: mobile subscriber data register equipment (5) for registering information regarding mobile subscribers (1) including subscriber numbers (N(1)) of the mobile subscribers (1), subscriber data of the mobile subscribers, identification numbers (PN(1)) of mobile stations (1), and location information of the mobile stations; base stations (2a, 2b) connected to subscriber lines of ISDN local switches (3a) through ISDN subscriber interfaces, and performing radio link control of said mobile stations (1) to connect calls which are originated from or terminated at the mobile stations (1) to said ISDN switched network (6) by way of the subscriber lines; and mobile subscriber connection control equipment (4) connected to a subscriber line of an ISDN local switch (3b) through subscriber interface, and to said mobile subscriber data register equipment (5), characterized in that said mobile communication system is adapted to first route calls which are originated from or terminated at the mobile stations (1) to said mobile subscriber connection control equipment (4) over said subscriber line of said ISDN local switch (2a), and said mobile subscriber connection control equipment (4) is adapted to thereafter complete the calls by re-originating said calls terminated at the mobile subscriber connection control equipment (4) over said ISDN switched network (6) through said ISDN local switch (3b) and designating a called subscriber as the terminating address, and when one of the mobile stations (1) during service transmits a channel switching request signal to one of the base stations (2a) which is in control designating an adjacent base station (2b) to which said one of the mobile stations (1) desires to be connected, said one of the base stations (2a) which is in control is adapted to originate a call to said mobile subscriber connection control equipment (4) to report the channel switching request along with the identification number (PN(1)) of said one of the mobile stations (1) and said channel switching request signal as additional information; said mobile subscriber connection control equipment (4) is adapted to originate a call to said adjacent base station (2b) to report information regarding the channel switching request and to instruct said adjacent base station (2b) to secure a radio channel for switching; said adjacent base station (2b) is adapted to store the identification number (PN(1)) of said one of the mobile stations (1) and to report a securing condition of a radio channel for switching to said mobile subscriber connection control equipment (4) using an alerting signal; said mobile subscriber connection control equipment (4) is adapted to instruct, when it confirms that the radio channel for switching has been prepared, channel switching to said one of the base stations (2a) which is in control using an alerting signal adding the information of the radio channel for switching; said one of the base stations (2a) which is in control is adapted to instruct said mobile station (1) to perform switching of the radio channel; said mobile station (1) is adapted to perform switching of the radio channel in accordance with the switching instruction; and said adjacent base station (2b) is adapted to report, after confirming the switching of the radio channel, to said mobile subscriber connection control equipment (4) using a signal of connection that the switching of the radio channel has been completed. A mobile communication system as claimed in claim 1 wherein, when an originating mobile station (1) of said mobile stations sends a call request for a fixed subscriber (7) to a base station (2a) designating a called subscriber number N(7) for said fixed subscriber (7) and adding an assigned identification number (PN(1)) of the originating mobile station, the base station (2a) is adapted to regenerate a call designating a subscriber number (N(4)) allocated to said mobile subscriber connection control equipment (4) as a called number and adding said called subscriber number (N(7)) and said identification number (PN(1)) as additional information, said mobile subscriber connection control equipment (4) is adapted to read out and analyze subscriber data of said mobile stations corresponding to said assigned identification number (PN(1)) from said mobile subscriber data register equipment (5), and to re-originate a call to said fixed subscriber (7); and when a fixed subscriber sends a call request designating a receiving subscriber number N(1) of one of said subscriber numbers as a called number, a call is first set up and terminated at said mobile subscriber connection control equipment (4), said mobile subscriber connection control equipment (4) is adapted to read out and analyze an assigned identification number (PN(1)) and a location information of a corresponding mobile station in accordance with the receiving subscriber number (N(1)) from said mobile subscriber data register equipment, to determine at least one base station to be seized, and to re-originate a call designating a subscriber number allocated to said at least one base station (2a) and adding the assigned station identification number (N(2a)) as additional information, and said at least one base station (2a) is adapted to alert one of the mobile stations (1) in accordance with the assigned identification number (PN(1)) to terminate the call at the one of said mobile stations. A mobile communication system as claimed in claim 1 wherein, when one of the mobile stations (1) detects a changing of a location registration area and transmits a location registration request signal to one of the base stations (2b) which belongs to the location registration area after the changing adding an assigned identification number (PN(1)) of one of said mobile stations (1), said one of the base stations (2a) is adapted to re-originate a call designating the subscriber number (N(4)) of said mobile subscriber connection control equipment (4) as a called number and adding said assigned identification number (PN(1)) and said location registration request signal as additional information, and said mobile subscriber connection control equipment (4) is adapted to refer to said assigned identification number (PN(1)) and the calling number (N(2b)) of said one of the base stations (2b) to update the location information of said one of the mobile stations (1) in said mobile subscriber data register equipment (4).

Inventors: OWADA JUNICHI, YAHAGI MASAHIKO, OWADA, JUNICHI, YAHAGI, MASAHIKO, OWADA, JUNICHI, C/O NEC CORPORATION, YAHAGI, MASAHIKO, C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1994
Main classification: H04Q7
IPC codes: H04W36